Stabilized acrylonitrile polymer compositions containing dibutyltin oxide and oxalic acid



United States Patent STABILIZED ACRYLONITRILE POLYMER CGM- POSITIONS CONTAINING DIBUTYLTIN ()XEDE AND OXALIC ACID Thomas M. Veazey, Wayne R. Eberhardt, and Ronald K.

Christensen, Decatur, Ala., assignors to Monsanto Company, a corporation of Delaware No Drawing. Filed Sept. 6, 1963, Ser. No. 307,002

8 Claims. (Cl. 26045.75)

This invention relates to a halogen containing polymeric composition which has been stabilized to color degradation due to both heat and light as well as the method of producing the composition. More specifically, it is related to a halogen containing acrylonitrile polymer composition which is stabilized to color degradation due to both heat and light as well as the method for producing this halo-gen containing acrylonitrile polymer composition.

Synthetic linear fibers are well known in the art and their valuable properties in the fiber and textile field are wellknown and recognized. There appears to be one problem which is common to most of these synthetic linear fibers and is particularly troublesome with those which contain halogen as an integral part of the polymeric structure and that is they degrade when exposed to light and heat. Many agents have been proposed and are known in the art to reduce this degradation to light and heat by incorporating them within the fiber during the spinning operation. However, most of these stabilizing agents merely reduce the extent of initial degradation during spinning and processing instead of continuing to protect against this discoloration or degradation during extended wear or use. In addition, with many of the known stabilizing agents which do impart improved and superior resistance to light and heat degradation over those fibers which do not contain the agents, the fibers thus produced are unsatisfactory when very light pastel colors are required, since the agents themselves impart an initial color to the fiber. Most of the synthetic linear acrylic fibers during their production acquire a slight yellowish cast or color which is most definitely objectionable to the textile industry. Most of this is due to the heat acquired during or immediately subsequent to the spinning operation. Among other methods for achieving a satisfactory inital color of synthetic fibers is by using textile bleaching agents, but most are unsuccessful in actual Wear in that while these conventional bleaching methods and agents have removed the initial discoloration, the fibers thus treated are not stable to ultra-violet light and generally become discolored in about two hours exposure. However, these same synthetic fibers possess excellent wash and wear or wrinkle resistant qualities along with warmth, a pleasing hand, a good wear resistance and a most desirous shape retention characteristic.

It is therefore the principal object of this invention to provide a method for producing synthetic linear halogencontaining fibers of acceptable whiteness.

Another object of this invention is to provide a method for producing halogen-containing fibers which are stabilized to degradation caused by light and heat.

Another object of this invention is to provide a synthetic halogen-containing fiber which retains its improved whiteness and color stability on exposure to ultra-violet light and heat.

Another object of this invention is to provide a method for improving the color and light stability of fibers or yarns composed of at least 80 percent acrylonitrile and up to 20 percent of another mono-olefinic halogen-containing copolymerizable monomer.

Another object of this invention is to provide a method for the improvement in color and light stability of fibers dfildflfifi Patented Apr. 11, 1987 "Ice composed of 85 percent acrylonitrile and 15 percent vinylidene chloride.

Another object of this invention is to provide a method for improving the color and light stability of fibers composed of a blend of copolymers and a halogen-containing homopolyrner, 85 to 90 percent of the blend being a copolymer of at least percent acrylonitrile and up to 20 percent of at least one other mono-olefinically unsaturated monomer copolymerizable therewith, and 15 to 10 percent of the blend being a homopolymer vinyl chloride.

Another object of this invention is to provide a fiber stabilized to degradation caused by light and heat, composed of at least 80 percent acrylo-nitrile and up to 20 percent of other mono-olefinic monomer; copolymerizable therewith, at least one of which is a halogen-containing monomer.

Another object of this invention is to provide a fiber stabilized to degradation caused by light and heat, composed of percent acrylonitrile and 15 percent vinylidene chloride.

Another object of this invention is to provide a fiber stabilized to degradation caused by light and heat, composed of a blend of a copolymer and a halogen-containing homopolymer, the blend being 85 to percent of a copolymer composed of at least 80 percent acrylonitrile and up to 20 percent of at least one other mono-olefinically unsaturated monomer copolymerizable therewith and 15 to 10 percent of a homopolymer of vinyl chloride.

Other objectives and advantages ancillary to the principal object that may be realized by the practice of this invention are manifest in the ensuing description and specifications.

Generally the object of this invention are accomplished by mixing with the polymer, prior to spinning, a blend of oxalic acid and dibutyltin oxide and, if desired, any conventional delusterant.

More specifically, a composition containing from 0.05 percent to 0.50 percent of oxalic acid and from 0.05 percent to 0.050 percent of dibutyltin oxide, based on the weight of the total polymeric compoistion is very thoroughly mixed with the fiber forming composition before it is extruded in filamentary form. This composition may be mixed with the polymer prior to it being dissolved in a conventional solvent such as dimethyl formamide, dimethyl sulfoxide, dimethyl acetamide, or the like, or the stabilizing composition may be added to the solvent first, blending very thoroughly and then having the polymer dissolved into the solvent, again blending very thoroughly and intimately. It is not at all essential that a delusterant be used but if used it is added as in conventional delustered synthetic fiber production. Once the dope, as the spinnable mixture is referred to in the art, is intimately and thoroughly mixed and blended, containing not only the polymer to be spun, but the stabilizing composition of oxalic acid and dibutyltin oxide and a solvent, it may be extruded into a conventional spin bath as is Well known in the field of wet spinning of synthetic fibers. The method of spinning is not germane to the inventive idea in the least. Once the synthetic linear fibers have been spun through their conventional spinning system, they are then processed in the usual conventional manner for distribution to various textile manufacturers. It is of importance in the method of this invention that the two stabilizing compounds, oxalic acid and dibutyltin oxide, be used together and intimately blended with the polymeric composition in order to stabilize the synthetic linear fibers produced therefrom.

While this application has been generally directed to halogen-containing synthetic linear fibers the method of this invention is especially useful in the stabilizing of fibers composed of halogen-containing, acrylonitrile based polymers. The polymeric materials which may be em- :ployed in the practice of the present invention are polyacrylonitrile, copolymers, including binary and ternary polymers containing at least 80 percent by weight of acrylonitrile in the polymer molecule, or ablend comprising polyacrylonitrile or copolymers comprising acrylonitrile with up to 50 percent of another polymeric material, the blend having an overall polymerized acrylomtrile content of at least 80 percent by weight.

While the preferred polymers employed in the instant invention are those containing at least 80 percent of acrylonitrile, generally recognized as the fiber forming acrylonitrile polymers, it will be understood that the invention is likewise applicable to polymers containing less than 80 percent acrylonitrile. They are useful in forming films, coating composition, molding operations, lacquers and also in forming the modacrylic fibers.

The halogen content of the polymeric composition may arise from the copolymerization of a halogen-containing mono-olefinically unsaturated monomer with another or other mono-olefinically unsaturated monomer which may or may not also contain halogen.

Suitable halogen-containing mono-olefinic monomers include alpha-chloroacrylonitrile, the methyl, ethyl, and butyl esters of alpha-chloroacrylic acid as well as the free acid, beta-chloroethyl methacrylate, vinyl chloroacetate, vinyl chloride, vinyl bromide, vinylidene chloride, l-chloro 1 bromo ethylene, alpha chloroacrylamide, alpha-chlorostyrene, alpha-bromocinnamic acid, the ring halogenated styrenes and other mono-olefinic halogencontaining compounds which are copolymerizable with acrylonitrile.

A preferred polymer of the instant invention comprises at least 80 percent acrylonitrile copolymerized with up to 20 percent of a halogen-containing mono-olefinic monomer.

The halogen content of the polymeric composition may also arise from the blending of two or more polymers, only one of which contains halogen. Polyacrylonitrile, for instance, or an acrylic copolymer of acrylonitrile and another monomer copolymerizable therewith may be blended in any convenient ratio with a halogen-containing polymer such as homopolymers of vinyl chloride, vinylidene chloride or other halogen-containing monomers as enumerated above, or binary or higher copolymers wherein at least one of the monomers contain a halogen as an integral part of the molecule. Examples of this latter category are vinyl bromide-vinylidene chloride copolymers and vinyl chloride-vinyl acetate copolymers.

Suitable non-halogen containing mono-olefinic monomers include acrylic and methacrylic acid and their esters such as butyl methacrylate and ethyl acrylate, acrylamide, methacrylamide, methacrylonitrile, methylvinyl ketone, styrene, cinnamic acid and itaconic acid and their esters, vinylbenzene sulfonic acid and its salt, amides and other derivatives, vinyl carboxylates, alkyl vinyl ethers and other mono-olefinic polymerizable materials.

The polymeric, fiber forming composition of the instant invention may comprise a binary, ternary, or higher interpolymer, for example, products obtained by the interpolymerization of acrylonitrile and one or more of any of the monomers, other than acrylonitriles, enumerated above at least one of which contains halogen. More specifically, such a ternary polymer might contain 85 percent of acrylonitrile, percent of a vinyl halide or a vinylidene halide and 5 percent of another substance such as methacrylonitrile or vinyl acetate.

The polymeric composition may also be a blend of polyacrylonitrile or of a binary or higher interpolymer of from 80 percent to 99 percent acrylonitrile and .from 1 percent to percent of at least one other C=C containing substance with from 2 percent to 50 percent of the weight of the blend of a halogen-containing homopolymer or copolymer of from 10 percent to 70 percent of acrylonitrile and from 30 percent to 90 percent of at least one other C=C containing polymerizable halogen-containing monomer. Preferably, when the polymeric material comprises a blend, it will be a blend of a copolymer of percent to 98 percent acrylonitrile and from 2 percent to 10 percent of another or other monoolefinic monomers, such as vinyl acetate, with a sufiicient amount of a halogen-containing polymer to provide the desired halogen content in the polymer blend.

The following examples are cited to illustrate the 1nvention. They are not intended to limit it in any way. Unless otherwise noted, percentages as expressed in the examples indicate percent by weight. The percentages of dope additives such as delusterants and stabilizers are based on the weight of polymer in the dope. In the color measurements given in the examples, the dominant wavelength (DWL) of all samples was 575i3.

Example 1 A dope composed of a copolymer of 85 percent acrylonitrile and 15 percent vinylidene chloride, a solvent, and a stabilizer composition composed of 0.15 percent dibutyltin oxide and 0.15 percent oxalic acid was wet spun using conventional techniques. The fibers thus produced had their color measured using a Spectrophotometer which showed the fibers possessed a purity of 6.8 and a brightness of 83.2. The fibers were then heated to C. for a period of 25 minutes and allowed to cool. The color of the fibers was again measured on a GE. Spectrophotometer which showed that the fibers possessed a purity of 7.6 and a brightness of 8.2.5.

Example 2 A dope composed of a copolymer of 85 percent acrylonitrile and 15 percent vinylidene chloride and a solvent, but without the stabilizing composition of Example 1 was wet spun using conventional techniques. The color of the fibers thus produced by using the dope without the stabilizing composition was measured using a GE. Spectrophotometer. The purity of the fibers thus produced was 12.1 and brightness 66.8. These fibers were then sub jected to heat at 145 C. for a period of 25 minutes and allowed to cool. The color was again measured using a GE. Spectrophotometer which showed that the purity was 13.1 and brightness was 67.9. Thus, when comparing the color of the fibers of this example against those of Example 1 in which the dope or color stabilizing composition was added to the dope prior to spinning, it is seen that the fibers containin the stabilizing composition are initially whiter in color by about 5 units in purity and 15 units in brightness and this color advantage is retained during exposure to elevated temperatures.

Example 3 A dope composed of a copolymer of 85 percent acry: lonitrile and 15 percent vinylidene chloride, a solvent, 4.0 percent of antimony om'de as a delusterant, and a stabilizing composition of 0.10 percent dibutyltin Oxide and 0.15 percent oxalic acid was wet spun using conventional wet spinning techniques. The color of the fibers thus produced was measured using a GE. Spectrophotometer which showed the fiber to have a purity of 5.3 and brightness of 74.3. These fibers were then heated at 145 C. for a period of 25 minutes and allowed to cool. The color was again measured using a GE. Spectrophotometer which showed the heated fibers to have a purity of 7.5 and brightness of 73.2.

Example 4 A dope composed of a copolymer of 85 percent acrylonitrile and 15 percent vinylidene chloride, a solvent, and 4.0 percent of antimony oxide as a delusterant but without the stabilizing composition of Example 3 was wet; spun using conventional techniques. The color of the fibers this produced was measured using a GE. Spectrophotometer. The fiber was shown to have a purity of 10.0, brightness of 75.0, and DWL of 577. These fibers were then heated at 145 C. for a period of 25 minutes and allowed to cool. The sample was again measured for color in the same manner and its heated fiber was found to have a purity of 12.8, brightness of 73.6 and DWL of 577.

In comparing the color of the stabilized (and delustered) fiber of Example 4, a color advantage of about 5 purity units is shown for the stabilized composition and again this color advantage is retained during exposure to elevated temperatures.

Thus it is seen with the stabilizing mixture of the present invention the acrylic fibers produced using this stabilizing mixture in the dope intimately mixed prior to spinning the fibers are resistant to degradation due to temperature or heat as well as possessing initially a considerably superior color as compared with similar unstabilized compositions. These fibers will thus more readily be capable of being dyed in light pastel colors as well as dark colors.

Example 5 A spinning dope composed of a blend of two polymers, the first being 87 percent of a terpolymer containing 95.3 percent acrylonitrile, 38 percent vinyl acetate and 0.9 percent of sodium p methallyloxybenzene sulfonate and the second being 13 percent of a vinyl chloride homopolyrner, a solvent, and a stabilizing composition consisting of 0.15 percent oxalic acid and 0.15 percent dibutyltin oxide was wet spun using conventional techniques. The fibers thus produced were exposed to a xenon are light in a Weatherometer for a total of 320 standard hours and the color determined by means of a GE. Spectrophotometer. The exposed fiber was found to have a purity 01": 5.0 and a brightness of 84.8.

Example 6 A spinning dope of the same composition as Example 5 except that the stabilizing ingredients were omitted was wet spun conventional techniques. The fibers thus produced were exposed to a xenon arc light in a Weatherometer for a total of 320 standard hours and the color etermined by means of a GE. Spectrophotometer. The exposed fiber was found to have a purity of 9.9 and a brightness of 77.1.

In comparing the color of the stabilized fiber of Example 5 with the unstabilized fiber of Example 6 after extensive Weatherometer exposure, it is again found, as with the heated samples of previous examples, that the stabilized fiber is whiter by about 5 purity units and, in case of the light exposed sample, has a brightness advantage of about 7 units. The color was again measured using a G.E. Spectrophotometer which showed the heated fibers to have a purity of 7.5 and brightness of 73.2.

It is understood that changes and variations may be made in the present invention by one skilled in the art without departing from the spirit and scope thereof as defined in the appended claims.

We claim:

1. A composition comprising a polymer composition blended with from about 0.05 to about 0.5 percent of oxalic acid and from about 0.05 to about 0.5 to about 0.5 percent by weight of dibutyltin oxide, said polymer composition being selected from the group consisting of acrylonitrile polymers blended with halogen containing addition polymers and acrylonitrile polymers having interpolymerized therewith halogen containing ethylenically unsaturated monomers.

2. The composition of claim 1 wherein said polymer composition is dissolved in a solvent.

3. A synthetic textile fiber comprising the composition of claim 1.

4-. The composition of claim ll wherein said polymer composition comprises a polymer containing at least about percent by weight of acrylonitrile and up to 20 percent by weight of a halogen containing ethylenically unsaturated monomer copolymerizable therewith.

5. The composition of claim 1 wherein said halogen contains ethylenically unsaturated monomer copolymerizable therewith is vinylidene chloride.

6. The composition of claim 1 wherein said polymer composition comprises an acrylonitrile polymer blended with from 2 to 50 percent by weight of a halogen containing addition polymer.

7. The composition of claim 6 wherein said acrylonitrile polymer contains at least 80 percent by weight of acrylonitrile and up to 20 percent by weight of an ethylenically unsaturated monomer copolymerizable therewith and the halogen containing addition polymer is polyvinyl chloride.

8. A method for producing heat and light stable articles which comprises blending a polymer composition, a solvent for said polymer composition, and from about 0.05 to about 0.5 weight percent based on said polymer composition of oxalic acid and from about 0.05 to about 0.5 weight percent based on said polymer composition of dibutyltin oxide to form a solution of said polymer composition containing oxalic acid and dibutyltin oxide and thereafter extruding said solution, said polymer composition being selected from the group consisting of acrylonitrile polymers blended with halogen containing polymers and acrylonitrile polymers having interpolymerized therewith halogen containing ethylenically unsaturated monomers.

References Qited by the Examiner UNITED STATES PATENTS 2,267,777 12/1941 Yngve 260-4575 2,739,140 3/1956 Price et al. 26045.85 3,088,932 5/1963 Tarkington et al. 26045.75

LEON J. BERCOVITZ, Primary Examiner.

R. W. RAUCHFUSS, Assistant Examiner. 

1. A COMPOSITION COMPRISING A POLYMER COMPOSITION BLENDED WITH FROM ABOUT 0.05 TO ABOUT 0.5 PERCENT OF OXALIC ACID AND FROM ABOUT 0.05 TO ABOUT 0.5 TO ABOUT 0.5 PERCETN BY WEIGHT OF DIBUTYLTINOXIDE, SAID POLYMER COMPOSITION BEING SELECTED FROM THE GROUP CONSISTING OF ACRYLONITRILE POLYMERS BLENDED WITH HALOGEN CONTAINING ADDITION POLYMERS AND ACRYLONITRILE POLYMERS HAVING INTERPOLYMERIZED THEREWITH HALOGEN CONTAINING ETHYLENICALLY UNSATURATED MONOMERS. 